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**High-Density Polyethylene Shell Prefabricated Direct-Buried Insulation Pipe – Application and Benefits**
Dacheng Xiangdong Insulation Refractory Material Factory | Phone: 13473696600 | 15731614448
This high-density polyethylene (HDPE) shell prefabricated direct-buried insulation pipe is designed with a three-layer structure, ensuring superior thermal insulation, protection, and durability. It's widely used in heating, cooling, and industrial applications across various sectors. Let’s take a closer look at its structure, features, and benefits.
The **first layer** consists of the working steel pipe, typically made from seamless pipes (GB8163-87), spiral welded pipes (GB9711-88; SY/T5038-92), or straight seam welded pipes (GB3092-93). Before installation, the steel pipe undergoes advanced shot blasting and descaling processes to achieve a surface cleanliness grade of Sa2 according to GB8923-1988 and a roughness level of R=12.5 microns per GB6060.5-88.
The **second layer** is the rigid polyurethane foam insulation, created by injecting raw materials into the space between the steel pipe and the outer sheath using a high-pressure foaming machine. This method is commonly referred to as "tube-in-tube foaming." The insulation layer serves multiple purposes: it prevents water ingress, provides thermal insulation, and supports the weight of the heating network. For temperatures ranging from -50°C to 120°C, this rigid polyurethane foam is ideal.
The **third layer** is the HDPE protective shell, pre-fabricated into a black or yellow plastic pipe with a specific wall thickness. It undergoes corona treatment to enhance adhesion and performance. Its main functions are to protect the polyurethane layer from mechanical damage, prevent corrosion, and ensure waterproofing.
This type of insulation pipe is suitable for a wide range of applications, including urban central heating systems, greenhouses, cold storage facilities, coal mines, oil ports, and chemical plants. However, it has some limitations. Compared to fiberglass-reinforced plastic (FRP), HDPE has lower heat resistance, typically up to 60–70°C, while FRP can withstand up to 100–120°C. Therefore, it’s important to consider the environment and temperature requirements before application.
**Key Advantages of HDPE Insulation Pipes:**
1. **Cost-Effective Construction**
Using HDPE as the protective layer can reduce construction costs by approximately 10%, while using FRP can cut costs by up to 25%. This makes it an economical choice for large-scale projects.
2. **Low Heat Loss and Energy Efficiency**
With a thermal conductivity of λ=0.013–0.03 kcal/m·h·°C, it significantly outperforms traditional insulation materials. Its low water absorption rate (around 0.2 kg/m²) and closed-cell structure (about 92%) ensure excellent thermal efficiency. This reduces overall heat loss, with network losses as low as 2%, well below the international standard of 10%.
3. **Excellent Corrosion Resistance and Long Lifespan**
The tight bonding between the polyurethane insulation and the steel pipe prevents moisture and air penetration, enhancing anti-corrosion properties. Combined with the durable HDPE or FRP outer shell, the service life can exceed 50 years—three to four times longer than traditional trench or overhead installations.
4. **Space-Saving and Eco-Friendly Installation**
Unlike conventional methods that require extensive trench digging, this system only needs underground burial. This reduces land use by over 50% and cuts earthwork and concrete usage by 90%. Additionally, on-site joint work can speed up the construction process by about 50%.
For more information or to discuss your project, feel free to contact Dacheng Xiangdong Insulation Refractory Material Factory.
**Source:** [http://news.chinawj.com.cn](http://news.chinawj.com.cn)
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